Authors:Sarah Fadden; Kate PriorPages: 375 - 379Abstract: Publication date: August 2017 Source:Anaesthesia & Intensive Care Medicine, Volume 18, Issue 8 Author(s): Sarah Fadden, Kate Prior Trauma is a significant cause of morbidity and mortality in the UK. Developments in the delivery of pre-hospital trauma care and advances in techniques for managing critically injured patients on scene, partly due to military medical experiences in recent conflicts, have encouraged greater scrutiny of the performance of these services. In addition to the unique environmental and logistical challenges posed by pre-hospital care, the injury and physiology patterns typically associated with trauma patients necessitate a specific approach to their assessment and treatment, whereby control of Catastrophic haemorrhage is prioritized before management of Airway, Breathing and Circulation issues (<C>ABC). The time-critical casualty needs to be recognized, and immediate life- or limb-threatening complications addressed promptly, with expedited evacuation to definitive hospital care. In 2011 the General Medical Council (GMC) approved Pre-hospital Emergency Medicine (PHEM) as a subspecialty of Emergency Medicine and Anaesthetics, thereby highlighting it as an area of medical expertise which requires training of its practitioners, as well as demonstration of competent, evidence-based, and meticulously audited practice.

Authors:Susan Hanson; Ashley Hanson; Dominic AldingtonPages: 380 - 382Abstract: Publication date: August 2017 Source:Anaesthesia & Intensive Care Medicine, Volume 18, Issue 8 Author(s): Susan Hanson, Ashley Hanson, Dominic Aldington Pain management in the pre-hospital environment is a priority following life- and limb-saving manoeuvres. Pain should be assessed, documented and managed according to a multimodal model. Even in the context of environmental challenges and limited resources, pharmacological, physical and psychological interventions can be used to provide effective analgesia and relieve suffering prior to and during transfer to hospital.

Authors:Jonathan Pearson; Jeremy Henning; Katherine WoodsPages: 383 - 385Abstract: Publication date: August 2017 Source:Anaesthesia & Intensive Care Medicine, Volume 18, Issue 8 Author(s): Jonathan Pearson, Jeremy Henning, Katherine Woods Trauma remains one of the leading causes of mortality and morbidity in the UK, is the primary cause of mortality in the first four decades of life and has a significant impact on the economy of the nation. In recent years the structure of trauma care has undergone significant restructuring. This article will review the reports that led to these changes, discuss the changes that have occurred and describe some of the anaesthetic management of this important group of patients.

Authors:Matthew Boyd; Damian D. KeenePages: 386 - 389Abstract: Publication date: August 2017 Source:Anaesthesia & Intensive Care Medicine, Volume 18, Issue 8 Author(s): Matthew Boyd, Damian D. Keene Shock is defined as the failure of the circulatory system to provide the organ perfusion and tissue oxygenation required to meet cellular metabolic demands. Traumatic shock is most commonly associated with haemorrhage, although non-haemorrhagic shock can be found in trauma in the form of cardiogenic or neurogenic shock. Over the last decade evidence has demonstrated that trauma patients have an acute traumatic coagulopathy (ATC) caused by the injury process itself. This has been fundamental to the development of the current approach to management of traumatic shock, known as damage control resuscitation (DCR). DCR encompasses three key resuscitative strategies, permissive hypotension, haemostatic resuscitation (the use of blood products as primary resuscitative fluids) and damage control surgery. The implementation of DCR alongside the creation of trauma networks has been revolutionary in the management of the shocked trauma patient. Current focus is on evolving and refining these strategies including identifying the subsets of patients at greatest risk as early as practicable following injury.

Authors:Andrew Clarey; Dominic TrainorPages: 395 - 400Abstract: Publication date: August 2017 Source:Anaesthesia & Intensive Care Medicine, Volume 18, Issue 8 Author(s): Andrew Clarey, Dominic Trainor Anaesthetists and critical care physicians involved in emergency care provision, must be equipped with the knowledge and skills to accurately assess and initiate treatment in patients with severe burns. This summary aims to review airway management and fluid resuscitation in addition to sedation and analgesic choices. Some of the dogma involved in current aspects of modern burns care will also be questioned.

Authors:Alison B Main; Andrew J HooperPages: 401 - 403Abstract: Publication date: August 2017 Source:Anaesthesia & Intensive Care Medicine, Volume 18, Issue 8 Author(s): Alison B Main, Andrew J Hooper Drowning is a frequent cause of accidental deaths and injuries, resulting in a significant but preventable global health problem. It is characterized by respiratory impairment due to submersion of the airway, or immersion of the body including the airway, leading to global hypoxic injury. Risk factors for drowning include inadequate supervision of children, recreational or occupational access to water, risk-taking behaviour and underlying medical conditions. Management priorities include rescue and basic life support, with an emphasis on rescue breaths and reversal of hypoxia. Compression-only cardiopulmonary resuscitation is not recommended in drowning victims. Supportive critical care is directed towards optimizing oxygenation and circulation, and preventing complications. Temperature control is important, as hypothermia complicates drowning and may limit the efficacy of resuscitative attempts when severe. Survival rates after cardiac arrest due to drowning are poor, and patients who are unconscious on admission to hospital have a guarded prognosis. Consequently public health initiatives to prevent drowning are important.

Authors:Bob Winter; Hina Pattani; Emma TemplePages: 404 - 409Abstract: Publication date: August 2017 Source:Anaesthesia & Intensive Care Medicine, Volume 18, Issue 8 Author(s): Bob Winter, Hina Pattani, Emma Temple With an annual incidence of 13 per million, around 40,000 people in the UK live with spinal cord injury (SCI). The extent of morbidity and mortality and thus quality of life, is highly dependent on meticulous management from the first point of contact with medical services. Treatment is focused on reducing the risk of further cord injury and prevention of secondary (penumbral) damage through avoidable complications. As key members of trauma, theatre, intensive care and pain teams, anaesthetists and intensivists play a crucial role in influencing patient outcome in both the acute setting and in managing patients with chronic SCI presenting for emergency or elective surgical intervention.

Authors:Jonathan D. Minton; David J. DalyPages: 410 - 413Abstract: Publication date: August 2017 Source:Anaesthesia & Intensive Care Medicine, Volume 18, Issue 8 Author(s): Jonathan D. Minton, David J. Daly Remote anaesthesia is the provision of anaesthesia and sedation outside the theatre environment. The diverse range of locations, procedures and patient groups can provide a challenge to the anaesthesia team. Anaesthetists must maintain the same high standards as in the operating room, which requires appropriate facilities and staff, as well as suitable pre and post anaesthesia care.

Authors:Robert McCahon; Jonathan HardmanPages: 418 - 420Abstract: Publication date: August 2017 Source:Anaesthesia & Intensive Care Medicine, Volume 18, Issue 8 Author(s): Robert McCahon, Jonathan Hardman Plasma expanders are used to restore the circulating volume of a hypovolaemic patient. Typically, colloids are used to expand the plasma volume, although combinations of hypertonic crystalloid and colloid have recently been used. The currently available colloids vary in their physicochemical, pharmacodynamics and pharmacokinetic properties. In particular, they differ in molecular weight, which partly determines their duration of action, and in their ability to expand the plasma volume. Dextran, hydroxyethyl starch and hypertonic colloid solutions improve oxygen flux within the microcirculation. Despite their benefits, the use of dextran and high-molecular-weight starches is limited by their negative impact on coagulation. In addition, these macro-molecules may also induce acute renal failure in susceptible patients. Current research focuses on the development of artificial oxygen carriers as plasma expanders. These substances, which include modified stromal-free haemoglobin and perfluorocarbon emulsions, are undergoing clinical trials.

Authors:Sudesna Chatterjee; Melanie J. Davies; Giridhar TarigopulaAbstract: Publication date: Available online 6 September 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Sudesna Chatterjee, Melanie J. Davies, Giridhar Tarigopula Diabetes is a chronic and progressive metabolic disorder characterized by hyperglycaemia. The two main types of diabetes are type 1 diabetes (T1DM) where there is complete lack of insulin and type 2 diabetes (T2DM) which may be due to a combination of insulin resistance and relative insulin deficiency due to impaired β-cell function. Good control of blood glucose near physiological limits is vital to reduce long-term microvascular and macrovascular complications of diabetes. Insulin replacement is a life-saving measure in individuals with T1DM whereas the mainstay of therapy in T2DM includes oral agents, non-insulin injectables (incretin mimetics) and insulin. In T2DM, the incretin mimetics and sodium glucose co-transporter 2 inhibitors have revolutionized recent treatment options by reducing blood glucose, promoting weight loss and improving β-cell function with improved cardiovascular outcomes associated with some of these agents. Despite the availability of several drugs to treat this chronic debilitating condition, the management of hyperglycaemia remains challenging. The role of diet, lifestyle changes and patient education is of paramount importance and should be pursued aggressively. This review will look at drugs currently used to optimize blood glucose control and briefly discuss the role of newer therapeutic agents.

Authors:Zoe Parry; Ross MacnabAbstract: Publication date: Available online 18 August 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Zoe Parry, Ross Macnab Thyroid disease remains very common. Knowledge of the implications of these diseases is essential for all anaesthetists as these patients are frequently encountered and may be at risk of complications at any stage, preoperatively, intraoperatively or postoperatively. This article focuses on disorders of thyroid function and their management, thyroid malignancy, surgery of the thyroid gland and the perioperative anaesthetic management of patients undergoing thyroidectomy.

Authors:Rebecca Summers; Ross MacnabAbstract: Publication date: Available online 18 August 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Rebecca Summers, Ross Macnab The thyroid gland secretes thyroxine (T4) and triiodothyronine (T3) in response to thyroid-stimulating hormone release from the anterior pituitary gland. Iodine is essential for the synthesis of thyroid hormones. T4 and T3 increase the basal metabolic rate, heat production, and help to maintain normal growth and development. Serum calcium levels are under very tight control. The majority of calcium is found in bones. Calcium and phosphate levels are maintained by four hormones – parathyroid hormone (PTH), calcitonin, vitamin D and fibroblast growth factor 23. PTH is produced by the parathyroid glands and its secretion is determined by serum calcium levels.

Authors:Henry Wang; Chandran JepegnanamAbstract: Publication date: Available online 17 August 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Henry Wang, Chandran Jepegnanam Phaeochromocytomas and paragangliomas (PPGL) are catecholamine-secreting neuroendocrine tumours arising from the chromaffin cells in the adrenal medulla. These tumours may be identified incidentally, as part of a work-up for multiple endocrine neoplasia or following haemodynamic surges during unrelated procedures. Advances in perioperative management and improved management of intraoperative haemodynamic instability have significantly reduced surgical mortality from around 40% to less than 3%. Surgery is the definitive treatment in most cases and laparoscopic resection where possible is associated with improved outcomes. Anaesthetic management of PPGL cases represents a unique haemodynamic challenge both before and after tumour resection. In this article we describe the physiology of these tumours, their diagnosis, preoperative optimization methods, intraoperative anaesthetic management and management of postoperative complications.

Authors:Michael McGinlay; Swamy MruthunjayaAbstract: Publication date: Available online 16 August 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Michael McGinlay, Swamy Mruthunjaya Diabetes is a complex, chronic metabolic disorder affecting approximately 8.5% of the adult population with the number of people living with diabetes worldwide having almost quadrupled since 1980. This increase has largely been attributed to global urbanization and lifestyle changes. Diabetes affects 10–15% of the surgical population. These patients are now frequently elderly, have complex medical co-morbidities and present for both high-risk elective and emergency surgery. This multisystem disease poses a significant challenge to both anaesthesia and surgery with diabetic patients demonstrating higher morbidity and mortality rates compared to their non-diabetic counterparts. As the management of diabetes becomes more complex, it is vital that the anaesthetist, as a member of the multidisciplinary team, remains up-to-date and plays a key role in patient optimization and perioperative glycaemic control. It is crucial that good glycaemic control is maintained throughout the perioperative period as this has been shown to correlate with positive patient outcomes. Patients themselves are well experienced in managing their own diabetes and should be involved in doing so whenever possible.

Authors:Niroshini Nirmalan; Mahesh NirmalanAbstract: Publication date: Available online 16 August 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Niroshini Nirmalan, Mahesh Nirmalan Understanding the general principles of homeostasis and its regulation in health and disease is key to managing patients in intensive care units and operating theatres. In these environments, it is crucial to realize that physiological control is a dynamic process aimed at achieving a balance between two opposing sets of factors. Whereas one set of factors (e.g. the sympathetic nervous system) attempt to increase a physiological variable of interest at any given time, opposing forces acting almost concurrently, (e.g. the parasympathetic nervous system) will result in the reduction in the value of this variable. The human body is a self-adapting system and as a result of its ability to adapt, new physiological ‘steady states’ will be reached and maintained even in diseases. This review will explore some of the concepts and pathways involved in the regulation of homeostasis in the immediate, intermediate and delayed time scales following an initial perturbation, emphasizing the dynamic nature of this regulation.

Authors:Ahmed Osman; Rhys ClaytonAbstract: Publication date: Available online 16 August 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Ahmed Osman, Rhys Clayton Adrenal glands are vital endocrine glands located above the kidneys bilaterally. They play a major rule in sodium and potassium balance. They regulate blood pressure and consequently tissue perfusion both directly, through vasopressor effect of renin–aldosterone–angiotensin system, and indirectly, through the effect on sodium balance. Glucocorticoids play a major rule in regulation of metabolism which affects almost all body tissues. Glucocorticoid release is regulated via the hypothalamic–pituitary–adrenal axis.

Authors:Jennifer Cade; James HanisonAbstract: Publication date: Available online 16 August 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Jennifer E. Cade, James Hanison The pancreas plays a vital role in coordinating and regulating digestion and nutrient metabolism, and does so via endocrine and exocrine processes. Insulin and glucagon are produced within the endocrine pancreas to not only achieve glucose homeostasis, but regulate protein and fat metabolism. Enzymes and zymogens are secreted in alkaline pancreatic fluid to aid digestive function. This article looks at how the pancreas achieves such precise synthetic and secretory functions, and reviews the physiology of the secreted hormones and enzymes.

Authors:Niroshini Nirmalan; Mahesh NirmalanAbstract: Publication date: Available online 15 August 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Niroshini Nirmalan, Mahesh Nirmalan Blood glucose concentrations are required to be maintained within a narrow therapeutic range in order to ensure the normal functioning of the body. This is accomplished through a complex, interactive, finely coordinated neuro-endocrine regulatory process. Hormonal control through the opposing actions of insulin and glucagon secreted by the islet cells of the pancreas serve as the primary response mechanism to avert post-prandial hyperglycaemia and fasting hypoglycaemia. In addition to this basic response, a range of endocrine mediators concurrently intervene, to enable the fine modulation of the process through a range of insulin-dependent and insulin-independent processes, which ultimately achieve glycaemic control by influencing tissue glucose uptake, glycolysis, glycogenesis, glycogenolysis and gluconeogenesis. More recent evidence supports a central, predominantly hypothalamic role initiated through nutrient (glucose, fatty acid) and hormonal (insulin, leptin, glucagon-like peptide-1) stimuli that influences glucose regulation by direct or indirect effects on skeletal muscle glucose uptake, islet cell insulin/glucagon secretion and hepatic glucose production.

Authors:Graham Nelson; Rhys ClaytonAbstract: Publication date: Available online 14 August 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Graham Nelson, Rhys Clayton Obesity is an increasing problem and its burden on healthcare resources is well documented. This article gives an overview of the physiological and pharmacological considerations when anaesthetizing the obese patient. It will look at key aspects of assessing obese patients, and planning and delivering a safe anaesthetic to them. Special areas of focus include correct drug dosing, as well as equipment, monitoring and environmental aspects involved in delivering the anaesthetic.

Authors:Susan HutchinsonAbstract: Publication date: Available online 2 August 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Susan Hutchinson Dental anaesthesia developed down a different pathway from the rest of anaesthesia. Techniques such as nasal mask anaesthesia in the sitting position were specific to dental surgery, which took place largely outside hospital in dental clinics. Now dental anaesthesia is confined to locations within the aegis of a hospital and anaesthetic techniques are similar to those in other surgical specialities. Dental surgery consists of extractions and conservation. Short procedures for the extraction of teeth may still be carried out in children using a nasal mask, but more difficult extractions in adults and children, or conservation procedures are best done with a laryngeal mask or endotracheal tube. Close liaison with the dental surgeon is imperative in the planning of the anaesthetic technique. The downward pressure applied to the mandible during the extraction of teeth may cause reduction in airway patency unless intubated, and the anaesthetist may need to support the jaw and head in order to provide counter-pressure, also preventing excessive movement of the neck. Patients needing general anaesthesia include children, those with allergy to local anaesthetics, and adults with special needs, as well as those adults who are likely to need surgical extractions with removal of alveolar bone. During the recovery phase, the airway has to be watched carefully as the potential for obstruction is increased due to stimulation and soiling of the larynx with bleeding. Paracetamol and non-steroidal analgesics are the mainstay of analgesia in combination with local anaesthetic infiltration and specific dental blocks. In addition, stronger analgesics such as tramadol may be required in adults who are having multiple extractions. It should be an aim to provide all dental surgery in a day case setting, and careful choice of the technique should make this possible for all but those with unstable cardiorespiratory disease.

Authors:Luay Kersan; Urmila RatnasabapathyAbstract: Publication date: Available online 29 July 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Luay Kersan, Urmila Ratnasabapathy Airway management is central to anaesthesia for maxillofacial surgery. Not only is there a shared airway to contend with, difficult airways are frequently encountered. The main pathologies that present for surgery include trauma, infection, cancer and craniofacial deformities. All of these may present an airway challenge in either elective or emergency settings but a similar approach to the airway can be used in all these scenarios. Other surgical procedures include dental extractions, temporomandibular joint (TMJ) arthrocentesis, salivary gland surgery and facial aesthetic surgery. It is vital that clear airway management plans including rescue plans are made at the outset. These must be communicated to the surgical and anaesthetic team in advance. Trauma is excluded as it will be covered in a separate review article.

Authors:Vera Sokolova; Dmitrijs SokolovsAbstract: Publication date: Available online 27 July 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Vera Sokolova, Dmitrijs Sokolovs Flexible fibreoptic intubation offers options of airway control in awake and asleep patients, in cases with limited or absent mouth opening and complex anatomy. It may be used as a first choice or a rescue technique. Despite its limitations, for example in situations with significant airway blood or secretions, and airway obstruction, it is a valuable core skill for every anaesthetist.

Authors:Ruth L. Mawhinney; Alan HopeAbstract: Publication date: Available online 27 July 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Ruth L. Mawhinney, Alan Hope Conscious sedation is an anaesthetic technique which helps patients tolerate dental and other procedures. Safe sedation requires attention to patient selection, the clinical environment, appropriate intraoperative and recovery monitoring, sedation technique, and postoperative management. Various drugs can be used either singly or in combination. Low doses of short-acting anaesthetic agents allow fine control of sedation and a greater chance of success. Where anaesthetic agents are used, inadvertent overdosage is a risk, and these drugs must be administered by an anaesthetist. Entonox and oral and intravenous benzodiazepines can be safely administered by appropriately trained practitioners. Key definitions include ‘sedation’ and ‘conscious sedation’.

Authors:Aravind Basavaraju; Kate SladeAbstract: Publication date: Available online 26 July 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Aravind Basavaraju, Kate Slade Dental trauma is a frequently reported complication related to the administration of general anaesthesia and is the most common source of litigation against anaesthetists. General anaesthesia involving direct laryngoscopy, a difficult airway, pre-existing poor dentition and prosthetic dental restoration are major risk factors for dental trauma. Central maxillary incisors are the most frequently damaged teeth. It is good practice to perform a preoperative oral examination, document the findings and communicate the risk of dental trauma to the patient. In the event of dental damage appropriate timely management will minimize dental morbidity.

Authors:Sumit Gajree; Kevin J. O'HareAbstract: Publication date: Available online 26 July 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Sumit Gajree, Kevin J. O'Hare Failure to identify a difficult airway can have serious consequences. It is essential that a thorough assessment of a patient's airway is made, including history and a focussed examination. It is known that the reliability of preoperative assessment is disappointing but positive findings will allow for an appropriate airway management plan to be devised in order to minimize airway-related complications. Despite this, situations will still occur where an unexpected difficult airway is encountered.

Authors:Cristina Niciu; Val Cunningham; Kevin FitzpatrickAbstract: Publication date: Available online 26 July 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Cristina Niciu, Val Cunningham, Kevin Fitzpatrick Facial trauma is common and can produce both physical and psychological problems for patients. Managing patients in both the emergency setting and elective theatre environment can be extremely challenging, so airway interventions should be carefully planned so the safest and most effective technique can be chosen. This may mean that direct laryngoscopy may not be the safest or most straightforward option and awake fibreoptic intubation, videolaryngoscopy, submental intubation or awake tracheostomy may be a better choice in a given set of circumstances. An understanding of common mechanisms of injury and pathologies and the likely difficulties that will be present are essential. Senior anaesthetic input and effective teamwork are required to provide excellent levels of care for these patients.

Authors:William J.D. Whiteley; Jonathan G. HardmanAbstract: Publication date: Available online 25 July 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): William J.D. Whiteley, Jonathan G. Hardman Pharmacokinetic analysis is an experimentally determined theory of how a drug behaves when in vivo. Volume of distribution, clearance and terminal half-life are defined. Compartmental modelling is introduced and some relevant graphs are described in this article. Applications of this theory in anaesthesia are considered.

Authors:Shruti Chillistone; Jonathan G. HardmanAbstract: Publication date: Available online 25 July 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Shruti Chillistone, Jonathan G. Hardman Drug elimination is the removal of active drug from the body. Metabolism takes place largely in the liver and produces water-soluble metabolites which can be excreted in the bile or urine. Metabolism may also produce active or toxic metabolites or a pharmacologically active drug from an inactive prodrug. Most volatile anaesthetics are excreted unchanged via the lungs. Drug elimination can be affected by factors such as first-pass metabolism, genetic variants and various disease processes. Knowledge of these processes will allow better prediction of pharmacokinetics in practice.

Authors:Ming WilsonAbstract: Publication date: Available online 9 June 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Ming Wilson Some concepts in anaesthesia can be explained by exponentials, logarithms, differentiation and integration. The aim of this article is to discuss these mathematical principles and demonstrate their importance in clinical anaesthesia.

Authors:David WilliamsAbstract: Publication date: Available online 9 June 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): David Williams This article summarizes the history and application of the Système Internationale (SI) of units. Non-SI units in common use in anaesthesia and standard units of digital information are also described.

Authors:Rahat Ghafoor; Faisal RasoolAbstract: Publication date: Available online 9 June 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Rahat Ghafoor, Faisal Rasool According to the World Health Organization about 450 million people suffer from mental and behavioural disorders worldwide, whereas depression has a lifetime prevalence of between 10 and 20%. Antidepressants are broadly divided into four main groups: tricyclic antidepressants (TCAs), selective serotonin reuptake inhibitors (SSRIs), atypical agents and monoamine oxidase inhibitors (MAOIs). Lithium is also occasionally used as an adjunct to treat refractive depression, but is more commonly used as a mood stabilizer in bipolar affective disorder. Antipsychotics are usually classified as ‘conventional’ antipsychotics or ‘atypical’ agents. The anaesthetist has to incorporate these agents in premedication and should anticipate their interactions with anaesthetic technique.

Authors:Gary Thomas; Elana OwenAbstract: Publication date: Available online 7 June 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Gary Thomas, Elana Owen Precise measurement of physiological parameters during anaesthesia is vital, and enables clinicians to deliver safe and appropriate care to patients. Monitoring devices are essential tools in the clinical environment, and accurate records of the measurements provided by these monitors must be kept. The physical parameter to be measured is known as a measurand. Examples of measurands in clinical practice include temperature, voltage and pressure. In the process of measurement, a measurand should be quantitatively compared with a predefined standard. The fundamental components of a basic measurement system consist of a sensor, signal, display at a human interface and a feedback loop. The signal or surrogate marker of a measurand is often processed before display. It is important that the output of a measurement system accurately reflects the value of the measurand. Challenges presented by measurement systems involve the maintenance of precision and accuracy. The input relative to output of a transducer is ideally linear in nature but is subject to hysteresis and drift making regular calibration essential. Outputs of measuring devices will also depend on their ability to respond to static or dynamic change. The readings obtained from measurement devices are also subject to human error.

Authors:Shruti Chillistone; Jonathan G. HardmanAbstract: Publication date: Available online 7 June 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Shruti Chillistone, Jonathan G. Hardman The pharmacokinetic properties of a drug comprise the relationship between its absorption, distribution and inactivation. The passage of drugs across cell membranes is a key part of most pharmacokinetic processes. The most important means by which a drug crosses cell membranes is passive diffusion, the rate of which is determined by molecular size, the concentration gradient, lipid solubility, degree of ionization of the drug and protein binding. Pharmacokinetic processes can be summarized and the time course of drug action can be predicted using mathematical compartment models. In a single-compartment model, a drug is evenly distributed throughout the plasma and tissues and eliminated in an exponential manner. However, multicompartment models make allowance for the uptake of drugs from the plasma by different tissues and for different flow rates to these tissues. Drug distribution across the placenta is a special case and considered separately. The placental membrane is a lipid barrier that is less selective than the blood–brain barrier, allowing the passage of lipid-soluble drugs more easily than water-soluble drugs. The distribution and rate of equilibration across the placenta are determined by placental blood flow and the free drug concentration gradient.

Authors:David G. LambertAbstract: Publication date: Available online 7 June 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): David G. Lambert Based on the diverse array of anaesthetic structures, a single anaesthetic target site seems unlikely. With the knowledge that anaesthesia likely results from central nervous system depression, it can be hypothesized that anaesthesia results from either enhanced inhibitory transmission or reduced excitatory transmission. Two main targets have been extensively described: GABAA receptors and N-methyl-d-aspartate (NMDA) glutamate receptors. On γ-aminobutyric acid (GABA) binding to GABAA receptors, an influx of Cl− results to produce hyperpolarization. With the exception of ketamine, xenon and nitrous oxide, all anaesthetic agents potentiate GABA-mediated conductance. On binding of the main excitatory transmitter glutamate, NMDA receptors gate an influx of Ca2+ and Na+. Ketamine, xenon and nitrous oxide inhibit this ion movement to depress excitatory transmission.

Authors:David WilliamsAbstract: Publication date: Available online 7 June 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): David Williams This article introduces essential concepts of electricity and magnetism relevant to anaesthesia. Simple analogies are used to explain current electricity and the action of electronic components in common use. The concept of electric and magnetic fields is introduced with examples of their practical application.

Authors:Kathryn Corrie; Jonathan G. HardmanAbstract: Publication date: Available online 7 June 2017 Source:Anaesthesia & Intensive Care Medicine Author(s): Kathryn Corrie, Jonathan G. Hardman The classification of drug interactions is first considered in this article, with an explanation of the terminology. Emphasis is placed on the importance of the topic in relation to the polypharmacy employed in anaesthesia and critical care. Pharmacodynamic interactions are then discussed. Further classification of these interactions is explained using examples of drugs in everyday use in anaesthesia and critical care medicine. Non-specific pharmacodynamic interactions are considered at some length, being the largest group of drug interactions that occur in anaesthesia. Synergy and summation are extremely relevant to anaesthetic practice and are employed in both induction and maintenance of anaesthesia everyday. The article then explains pharmacokinetic interactions under the headings of absorption, distribution, metabolism and elimination. Again, emphasis is placed on drugs used in current practice to highlight the relevance of each type of interaction to the reader.